I was using a 10 metre length of hose on a sunny day. I couldn’t help noticing how warm the water was that came from it. After all it had only been out 10 minutes. I refilled the hose and left it for half an hour. 4.20pm now – I’ll wait until 4.50 and see if I can grab a quick hot shower before my girlfriend gets home.
I dashed out into the garden and stripped off, hoping my next-door neighbour wasn’t watching from the window. I got 12 seconds of warm water and the temperature changed quite quickly back to cold – too quickly. Over the next few days I let the sun heat up the water a few times on the roof and experimented with nozzle attachments. The shower nozzle was ideal but it went through the hot water too quickly. The spray device nozzle made the water last longer but it didn’t stay as warm, probably because the water droplets became a mist that cooled quicker in the air. Also critical was the time of day – the higher and hotter the sun, the better.
It occurred to me that if I could get a free, hot, 12 second shower from 10 metres of hose, then all I needed was more hose for a longer shower. I had another 40 metres elsewhere which I collected – although I did go and look in shops for all-black hosepipe which would absorb the heat more efficiently – I couldn’t find any.
I decided to spiral the hose on a black painted panel and got a bit carried away because I made three as you can see in the picture. I painted them black and put the home-made solar panels on the roof of the garage because it got more sun. I joined the panels into the gardening watering system, using plastic pipe sections with taps so I could isolate the panel to warm up and still use the garden hose if I needed.
In the mean time I found the black plastic water bags called ’20 litre solar camping shower bags’ that are quite popular and ordered one. According to the sales literature after an hour of full sun they give a shower of 26ºC, two hours gives 32ºC and three hours gives 40ºC – a nice warm shower. Unfortunately I ripped it open on the first us, when attempting to get a 5 gallon bag full of water high up enough to create a gravity feed!
When I tried out the new panels there was a slight haze over the sun and an ambient temperature in the shade of 15ºC. I didn’t have a shower but filled up the washing-up bowl, about 2 gallons, to reveal water at a temperature of 43ºC – a full 115ºF (for old fashioned folk). Fantastic.
The next day was even sunnier, without a heat haze and the water reached 47ºC. We refilled the panel several times and had free washing up water. Sarah had a shower that went on for ages (sorry I didn’t time it or photograph it – I was the shower bracket). As the season progresses these showers are getting even warmer and our washing-up water is free on sunny days.
I have now purpose built another one of these to heat our paddling pool in the summer.